The present invention relates to new cis-bicyclo[3.3.0]octane derivatives, to pharmaceutical compositions containing these new compounds for oral or parenteral administration and also to processes for preparing these new compounds and for using the compositions. The new cis-bicyclo[3.3.0]octane derivatives according to the invention correspond to the general formula: ##STR3## in which the phenyl radical has the EZ- or the E-configuration with respect to the double bond and in which the carbon atom which at carried the group R.sub.2 (and others) the molecule has the RS- or S-configuration.
In formula I, R.sub.1 represents a hydrogen atom, a straight or branched alkyl group containing 1 to 4 carbon atoms or a pharmaceutically acceptable cation. Preferably R.sub.1 represents hydrogen, a methyl or an ethyl radical or, if it represents a cation, a sodium or a potassium cation. Other suitable cations are known from their use in the chemistry of prostaglandins or prostacyclin, respectively.
R.sub.2 represents a cyclohexyl or 4-methyl cyclohexyl radical or a 1-adamantyl group of the formula: ##STR4## wherein R.sub.3, R.sub.4 and R.sub.5 have the same or a different meaning and each represents hydrogen or methyl.
Preferably the radicals R.sub.3 to R.sub.5 represent hydrogen. In preferred compounds of formula I, R.sub.2 represents the group: ##STR5## wherein R is hydrogen or methyl. The unsubstituted cyclohexyl group (R=H) is especially preferred.
The compounds of formula I have valuable pharmacological properties. In particular, they have blood platelet aggregation inhibiting effects (in-vitro and in-vivo) and also blood pressure lowering activity, i.e. they have prostacyclin-like properties. They distinguish, however, from prostacyclin, for instance, in that they are more stable than prostacyclin. There are known already chemically relatively stable analogs of prostacyclin such as carbacyclin (which like the compounds of formula I contains the cis-bicyclo[3.3.0]octane moiety) but the activities of prior analogs are only of short duration when used in-vivo [c.f. Whittle et al., Prostaglandins 19 (1980), 605-627, especially page 623].
U.S. Pat. No. 4,306,076 (Example 13) discloses the E- and the Z-forms of 1,5-inter-m-phenylene-2,3,4-trinor-carbacyclin, i.e. of 3-(m-carboxybenzylidene)-6-beta-(3'S-hydroxy-1'E-octenyl)-7-alpha-hydroxy- cis-bicyclo[3.3.0]octane. The EZ-form of this compound (hereinafter referred to as "compound A") was used as an additional comparison compound in some of the tests described hereinafter. As can be seen from the test results, the compounds of formula I, especially those with R.sub.2 =cyclohexyl, also show superior effects in comparision to those produced by compound A.